1. Field of the Invention
The present invention discloses a method of calibrating soft data of multimedia data streams, a soft demapper and a multimedia data stream calculating system, and more particularly, to a method of calibrating soft data by a scaling factor corresponding to lowest bit error rate (BER), a soft demapper utilizing the mentioned method above, and a multimedia data stream calculating system utilizing the provided soft demapper.
2. Description of the Prior Art
With respect to multimedia data streams propagated in digital television (TV) channels, an ideal Gaussian Model is usually applied in the simulations of channel (propagation) models for various channel signals. However, if the digital TV signals are propagated in high-density urban areas or fully scattering environments, the simulation results according to the ideal Gaussian Model may have significant errors or deviations compared to real channel propagation models of various digital TV channel signals.
Generally, multimedia data stream of digital TV signal contains soft data, which is simulated and computed according to Gaussian Model. Hence, when simulation with Gaussian Model have significant deviations/errors compared to that in real situation in digital TV channel signal propagations, the correctness of data detection in multimedia data streams can be deteriorated seriously, and broadcasting quality of multimedia data stream in the digital TV signals by digital TV is also downgraded in consequence.
Please refer to FIG. 1, which illustrates a signal strength diagram with respect to signal propagation of digital TV channels simulated according to a non-ideal channel model. As shown in the FIG. 1, a simulated signal strength ceiling SUP is generated when Gaussian Model is used to simulate channel model of the digital TV signal. For digital TV signal receiver, in high-density urban areas or fully scattering environment, frequency variation of received signal (or symbol) can be overly large (the phenomenon is called fading), such that the signal strength of real digital TV signal RL may exceed the simulated signal strength ceiling SUP. Under such circumstances, the signal strength exceeding SUP is treated as the simulated signal strength ceiling SUP in Gaussian Model simulation. As a result, obvious errors are induced after the signals exceeding the ceiling SUP are converted to soft data. And playing quality of digital TV signal would be seriously downgraded in consequence.
From the above it is clear that prior art still has shortcomings. In order to solve these problems, efforts have long been made in vain, while ordinary products and methods offering no appropriate structures and methods. Thus, there is a need in the industry for a novel technique that solves these problems.